Loops and PHP Decision Making - Breaking out
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If you want only the code in the matching block to execute, place a break keyword at the end of that block. When PHP comes across the break keyword, processing jumps to the next line after the entire switch statement. Example 4-11 illustrates how
processing works with no break statements.
Example 4-11. What happens when there are no break keywords
$action = "ASSEMBLE ORDER";
switch ($action) {
case "ASSEMBLE ORDER":
echo "Perform actions for order assembly.<br />";
case "PACKAGE":
echo "Perform actions for packing.<br />";
case "SHIP":
echo "Perform actions for shipping.<br />";
}
If the value of $action is "ASSEMBLE ORDER", the result is:
Perform actions for order assembly.
Perform actions for packing.
Perform actions for shipping.
However, if a user has already assembled an order, a value of "PACKAGE" produces the following:
Perform actions for packing.
Perform actions for shipping.
Defaulting
The SWITCH statement also provides a way to do something if none of the other cases matches, which is similar to the else statement in an if, elseif, or else block.
Use the DEFAULT: statement for the SWITCH's last case statement (see Example 4-12).
Example 4-12. Using the DEFAULT: statement to generate an error
switch ($action) {
case "ADD":
echo "Perform actions for adding.";
break;
case "MODIFY":
echo "Perform actions for modifying.";
break;
case "DELETE":
echo "Perform actions for deleting.";
break;
default:
echo "Error: Action must be either ADD, MODIFY, or DELETE.";
}
The switch statement also supports the alternate syntax in which the switch and endswitch keywords define the start and end of the switch instead of the curly braces {}, as shown in Example 4-13.
Example 4-13. Using endswitch to end the switch definition
switch ($action):
case "ADD":
echo "Perform actions for adding.";
break;
case "MODIFY":
echo "Perform actions for modifying.";
break;
case "DELETE":
echo "Perform actions for deleting.";
break;
default:
echo "Error: Action must be either ADD, MODIFY, or DELETE.";
endswitch;
You've learned that you can have your programs execute different code based on conditions called expressions. The switch statement provides a convenient format for checking the value of an expression against numerous possible values.
Next: Looping >>
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 This article is excerpted from chapter four of the book Learning PHP and MySQL, Second Edition, written by Michele Davis and Jon Phillips (O'Reilly, 2006; ISBN: 0596101104). Check it out today at your favorite bookstore. Buy this book now.
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